Additive manufacturing processes, such as fused filament fabrication, may be employed to form printed objects in a range of shapes. It is sometimes desirable to form conductive traces upon the surface of a printed object. Conductive traces and similar features may be introduced in conjunction with fused filament fabrication processes by incorporating a metal precursor in a polymer filament having a filament body comprising a thermoplastic polymer, and forming a printed object from the polymer filament through layer-by-layer deposition, in which the metal precursor remains substantially unconverted to metal while forming the printed object. Suitable polymer filaments compatible with fused filament fabrication may comprise a thermoplastic polymer defining a filament body, and a metal precursor contacting the filament body, in which the metal precursor is activatable to form metal islands upon laser irradiation.